On August 11, Kyushu Electric Power Company's 846 megawatt (MW) Sendai Nuclear Power Station Unit 1 became the first reactor to restart after nearly two years with no generation from nuclear power plants in Japan. Following the disaster at Fukushima in 2011, Japan began a temporary shutdown of all nuclear power plants as each reactor entered scheduled maintenance and refueling outages. By September 2013, all 54 reactors in Japan's nuclear fleet were shut down. Following its restart, Sendai Unit 1 will begin generating electricity within days and return to normal operation in early September.

The restart of Japan's nuclear power plants requires the approval of both Japan's Nuclear Regulation Authority (NRA) and the central government, as well as consent from governments of the local prefectures. In July 2013, the NRA issued more stringent safety regulations to address issues dealing with tsunamis and seismic events, complete loss of station power, and emergency preparedness. Currently, the NRA has approved the restart of five reactors: Sendai Units 1 and 2, Kansai Electric Power Company's (KEPCO) Takahama Units 3 and 4, and Shikoku Electric Power Company's Ikata Unit 3. Sendai Unit 2 will likely be the second reactor to restart, with an anticipated restart date in October. Although the Kagoshima Prefecture approved the restart of Sendai Units 1 and 2, the Fukui Prefecture continues to oppose the restart of Takahama Units 3 and 4. Ikata Unit 3 could restart in early 2016 if approval is received from Ehime Prefecture.

Beyond these 5 reactors, 19 of Japan's remaining 38 operable reactors have filed restart applications with the NRA that are in different stages of the review process. The total capacity of reactors under review is about 18,400 MW. There is still some uncertainty about whether some of these reactors can meet the new NRA regulations, particularly with respect to the ability to withstand severe earthquakes.

Source: U.S. Energy Information Administration

Before the 2011 earthquake and tsunami, Japan had 54 operating reactors. Following the disaster at Fukushima, all six Fukushima reactors, totaling about 4,500 MW, were permanently shut down. In April 2015, five additional relatively old, small reactors, totaling about 2,100 MW, were permanently shut down.

Japan was the world's third-largest producer of nuclear power (after the United States and France) before the disaster at Fukushima, and Japan's nuclear power plants historically accounted for about 30% of the country's total electricity generation. The gradual displacement of all of Japan's nuclear generation as the country's nuclear fleet was shut down resulted in increased dependence on liquefied natural gas, oil, and coal to make up the difference. The replacement of nuclear generation led to higher electricity prices for consumers, higher government debt levels, and revenue losses for electric utilities. As part of Japan's long-term energy policy, the central government has called for the nuclear share of total electricity generation to be 20–22% by 2030.